Synthesis And Properties Of 5-Arylthianthrenium Salt Cationic Photoinitiators Containing Polysiloxane And Preparation Of Silicone-Epoxy Hybrid Polymer By The Click Reaction

In recent years, there have been many researches on polysiloxane-modified macromolecular photo initiators that have self-floating capability and can be applied in the preparation of gradient polymers, surface coatings, powder coatings, optical fiber coatings, etc. However, most of the reported polysiloxane-modified macromolecular photoinitiators are free radical photoinitiators that only are used in free radical photopolymerization systems to initiate polymerization of acrylate monomers. The macromolecular cationic photoinitiators containing polysiloxane that can initiate cationic gradient photopolymrerization are rarely reported currentlyThis work has synthesized three kinds of polysiloxane-modified macromolecular cationic photoinitiators based on polysiloxane with low surface tension and low surface energy, and 5-arylthianthrenium salt cationic photoinitiator (1187) that is environmentally friendly and non-toxic. The photoinitiators can self-float up in cationic photopolymeriz-ation systems to form a gradient distribution from the bottom to the top, thereby initiating a gradient polymerization. This research expands the types and application fields of organosiloxane macromolecular photoinitiators.Thiol-click photopolymerization reaction is known as fast, efficient and insensitive to water and oxygen, and has a very broad application prospect in the fields of drug, biological macromolecules preparation, polymer modification and so on. The study explored a new method to prepare silicone-epoxy hybrid polymer materials by the thiol-click reaction. Meanwhile, polysiloxane-epoxy hybrid polymer materials with gradient composition were prepared by the thiol-click photopolymerization technology. The main study work and conclusions are as follows: 1. Three kinds of 5-arylthianthrenium salt cationic photoinitiators containing polysiloxane (1187-Si-A/B/C) have been synthesized through the esterification reaction of single carboxyl-ended polysiloxanes with 5-arylthianthrenium salt (1187). Their structures were confirmed by nuclear magnetic resonance (NMR) and fourier transform infrared spectroscopy (FTIR). The effect of the structure and concentration of the photoinitiator, the light intensity and monomers on the photopolymerization kinetics was discussed in detail. The self-floating capability and property of initiating gradient photopolymerization for three cationic photoinitiators containing polysiloxane were explored by ultraviolet-visible spectroscopy (UV-vis), gel permeation chromatography (GPC), contact angle tester (CA) and pencil hardness tester. The results show that compared to 1187, 1187-Si-A/B/C have excellent compatibility and photoinitiating activity in the epoxy monomer BADGE. They have absorption peaks at 240 nm,260 nm and 320 nm, and the peak at 240 nm is the strongest.1187-Si-A/B/C can quickly initiate the polymerization of the epoxy monomers. 1187-Si-A/B/C with good self-floating capability can spontaneously form a gradient distribution in the cationic photopolymerization system and initiate photopolymerization of the epoxy monomer to get a molecular weight gradient polymer. As the polysiloxane chain length (molecular weight) of 1187-Si-A/B/C increased, the photoinitiating rate and the final epoxy conversion were decreased, but the trend of the gradient polymerization became more obvious.2. The silicone-epoxy hybrid polymer networks were prepared with isopropyl thioxanthone (ITX) as a sensitizer, and TBDHBPh4 as a photo-base generator. The influence of compositions of the hybrid systems on the polymerization kinetics, and the dynamic thermal performance, thermostability, mechanical properties, surface properties and surface microstructures of hybrid polymers were investigated in detail. The results show that the hybrid polymer films of the thiol-epoxy and thiol-polysiloxane methacrylate have better thermostability and lower glas transition temperature that was decreased from 63.2? to 42.4? than the pure thiol-epoxy polymer film due to the introduction of the polysiloxane. Moreover, for the hybrid polymer films, the elongation at break was increased from 4.8% to 30%, but the tensile modulus and tensile strength were decreased. The contact angles of the hybrid polymer films were increased from 66.3° to 99.4°, while their water absorptions were reduced from 1.9% to 0.3%. Furthermore, the pencil hardness of the hybrid polymer films was decreased from 6H to 1B.3. The polymer hybrid materials (PETMP-EPOXY/PETMP-PSDMA) with a gradient composition were prepared by the thiol-click photopolymerization technology based on self-floaying capability of polysiloxane. The influence of the composition of the system on the viscosity of the system, thermostability, glass transition temperatures, the hardness, and surface properties and microstructures of the gradient polymer materials was systemically investigated. The results show that with the introduction of polysiloxane, the viscosity of PETMP-EPOXY/PETMP-PSDMA system was reduced almost 3 times. Tmax2, carbon residue rate and contact angle of the prepared gradient hybrid polymer rod were gradually increased from the bottom to the top, while the glass transition temperature and hardness were gradually descended.